J. ray. Army med. Cps. 1974,120, 102-108

ACUTE PULMONARY OEDEMA AT HIGH AL TIlUDE

Major K. HEDGES, M.Sc., M.B., Ch.B., D.T.M.&H., D.I.H., R.A.M.C. Headquarters, 3rd Division, Bulford Camp

SUMMARY: An incident of acute pulmonary oedema occurring in a Junior Guardsman at an altitude of 13,000 feet is described.

A review of the present knowledge of this condition is presented together with current views upon the early recognition and management of a case presenting on the mountainside and the rationale of prevention.

Introduction

" In the next few hours (his) breathing became progressively more congested and laboured. He sounded as though he were literally drowning in his own fluid, with an almost continuous bubbling sourid as if breathing through liquid. A couple of hours after his death ... I noticed that a white froth ... had appeared well up out of his mouth."

This vivid description by a non-medical correspondent prefaced the first docu­mented report of a case of acute pulmonary oedema published in English (Houston 1960).

The only statistical record of pulmonary oedema at altitude in the British Armed Services occurred 'on the 1970 Annapurna Expedition. This officer survived only to be killed the following year in Northern Ireland. His case was distinctive in being a relapse of an earlier episode which had developed whilst training in Switzerland in 1969 and is unusual in being one of the few documented cases reported in Europe (Milne 1973). There has, for example, been no known case on the Matterhorn-14,679 feet (Cerretelli 1972), although it is considered possible that some cases of pulmonary congestion recorded by Mosso (1898) and by Durig and Zuntz (1904), to in fact have been descrip­tions of acute pulmonary oedema occurring at altitude in the European Alps.

Several incidents of acute pulmonary oedema have however recently occurred amongst British servicemen whilst engaged upon energetic and demanding pursuits on Mount Kenya (Snyder 1973). These include a Marine in October 1971, and a member of a Royal Air Force Mountain Rescue Team in March 1973, both of whom had arrived on the mountain within days of leaving sea-level.

A paratrooper who had ascended to 15,700 feet on the second day after leaving sea-level died in respiratory failure whilst being carried off the mountain (Woodley 1972). The apparently high number of cases of pulmonary oedema on this mountain is almost certainly a function of its accessibility vis-a-vis other high mountains of the world.

An account of acute pulmonary oedema on Mount Kenya

A Junior Guardsman, M. R., aged 16, arrived at Base Camp (8,000 feet) towards the end of the millet harvest season (January to March), a period generally reckoned to be a good time for travel on the mountain (Mitchell 1971). Although the Anopheline mosquito is not found at this height, M.R .. was taking malarial prophylaxis, Proguanil Hydrochloride tablets BP 0.1 g daily, and spent some three weeks in the Base Camp

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K. Hedges 103

area as part of an advance party for a larger project. Table I shows the average weather profile during this period at Nanyuki 0' 01 ° N, 3T 04° E, March 1973, and it will be seen that this represents little, if any, heat SlTess. During his stay M. R. had become well­tanned by regular and graduated exposure to sunlight and was in excellent physical shape.

Table 1

Average weather profile at Nanyuki, March 1973

Average daily temperature Average relalive humidity

Maximum Minimum 0800 hours J400 hOllrs

77 degrees 49 degrees 66 degrees 33 degrees

M.R. and his group began their ascent. on Mount Kenya by driving to the road head at 9,600 feet. From there, the march began and at night fall the party reached its highest point at 13,000 feel. M.R. fell perfectly well at this time, although several of his companions \-vere complaining of mild frontal headache. Water was not plentiful, only 4 pints being consumed during the thirty-six hour trek.

During the evening, M.R. began t.o feel listless and weak and remembers having some difficulty in understanding when people spoke to him. He had no appetite and was noted to look pale and have bloodshot eyes. Although not noticed at the time, M.R. subsequently admitted on direct questioning that his breathing had become irregular, he had noticed himself sighing. Perhaps most significant, and a fact which he had not realised to be so, was that he could hear bubbling noises in his cb est. He did not sleep well during the night stop and began the next day with a dry cough. During the descent he felt greatly fatigued and vomited once before returning to the Base Camp at 8,000 fcet, some 36 hours after having first left it. For the next four days he felt ofT colour and was at times disoriented. He was therefore taken to Nanyuki Cottage Hospital , where he was found on admission to be cyanosed and to have rales in the right lower lobe. He was apyrexial and no other abnormal signs were elicited. A diagnosis or Pulmonary Oedema was made and the patient responded to Frusemide (Lasix) 40 mg tablets, two every 6 hours with a steady clinical improvement and moderate diuresis, being discharged two days later.

Figure I shows British Troops climbing at 13,500 feet towards the snow-covered peaks of Mount Kenya. The unique giant vegetation (Senecio brassica, the" Cabbage Groundsel ") is found only within the zone, 10,000 to 14,000 feet.

Discussion

Pulmonary oedema is an abnormal accumulation of liquid in the extra·vascular tissues and spaces of the lung (Robin et al 1973). There are many causes for this disorder amongst which arc listed left ventricular failure, mitral stenosis and non·cardiae con­ditions such as pulmonary embolism, parenchymal lung disease, narcotic overdose and most recently, exposure to high altitude (Brit. med . .I. 1973).

Mosso (1898) had first described the phenomenon of a changed breathing rhythm at. altitude, known as Cheyne-Stokes Breathing, which in other circumstances "A

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104 Acu/e Pulmol1ary Oedema a( High Allifllde

Fig. 1. British tfOOpS climbing at 13,500 fecL

physician would say . .. that they were of a dying person," This is panicularly noticeable at sleep and is often experienced by nOIl-acclimatised individuals who may wake up due to discomfort and distress associated with breathing (Folk 1966).

Monge' s pioneer work ill circulatory dynamics ( 1928) observed that the physiological consequence of exposure to altitude in some subjects resulted tragicaUy when the victim .. drowns in his own blood,"

Horrobin (1972) has speculated that it may be significant that 9,000 feet below which altitude-induced pulmonary oedema is ve ry rare. is the alLitude at which hypoxia begins to dominate the control of ventilation in the presence of a reduced arterial Peo2' This in turn triggers mechanisms which tend lo lead to a shift of circulating blood to the pulmonary capillary bed.

Singh's report (1969) of 1,925 physically fit men who were incapacitated following their arrival at altitudes above 11 ,000 feet, is at present the largest series to be published. He considers that Acute Mountain Sickness and High Altitude Pulmonary Oedema are clinical variants of the same disorder and found that a patient may suffer from either one or both illnesses. Concurrently with the development of pulmonary congestion, there was an almost invariable antidiuresis (physiological retention of watcr)- therapy against which prevents as well as relieves the illness.

Hultgren (1961) in a sllldy in the Peruvian Andes, raised the possibility that people who re-entered an altitude to whieh they were previously acclimatised were predisposed to pulmonary oedema. This unexpected observation is not, however, confirmed by Singh (1969) and it seems probable that there is no statistically significant relationship.

The mechanism by which pulmonary oedema occurs in some people at moderate and high altitudes is lhe subject of much complex debale and an increasing volume of field research.

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K. Hedges 105

There arc many uncertainties concerning the net effect of forces which produce fluid shifts across the alveolar-pulmonary-capillary compartments of the lungs. These have been surveyed with immense regard for detail in a recent article by Robin et al (1973).

At the present state of knowledge perhaps all that can be said is that an individual who has proved to be susceptible to altitude-induced pulmonary oedema is predisposed to a recurrencc if he again returns to altitude. There arc, however. many exceptions to this GO nOI only between individuals but in the same individual from time la lime." (Houston 1972).

Recognition and treatment

The onsel of pulmonary oedema on the mountainside is confused not only by the presence of the common features of acute mountain sickness, but also by the probable contingency that the vigilance and judgement of other members of the party may also be affected. In which case, the condition may be unrecognised unlil it is realised tbat one of the party is in fact seriously ill.

It is known that the early radiological signs of pulmonary oedema precede the clinica l presentation of dyspnoea (West 1970). The knowledge of this might appear to be academic half ",-ay tip a mountain when the whole party is Jikely to be breathless from exertion at unaccustomed altitude and where reliance in a diagnosis in any case must he placed upon unaided clinical acumen. H owever, this does corroborate Houston's (1973) preliminary communication on the present Mount Ranicr studies wbere early signs of fluid in the lungs, as determined by ausculalion, were found in 22 per cent of those reaching 12.000 feet.

The roint to be made is that effective treatment must be based upon ear)y recog­nition of pulmonary oedema occurring at altitude. The first step then is to be aware of the hazard. Pulmonary oedema may be present with or without other aspects of altitude sickness and has been seen to occur mostly in the individual who Teaches 10,000 feet within a few days of leaving sea level. There is a general feeling thut an increased suscep­tihility may exist for the young climber who is in good shape physically and who is able therefore to display considerable vigour during the climb. This view is held most strongly in East Africa where the condition has never been known to occur in a female (Snyder 1973), and not a single case has been reported on Mount Kilimanjaro which is in fact the highest mountain in Africa (Woodley 1973). This is believed to be due to the slow rate of ascent.

It is important to point Ollt, however. that other workers, and particularly the current Ranier studies, have indicatcd that there is little if any relationship between at;e. sex. physical condition, smoking and previous altitude experience.

Almost pathognomonic are bubbling noises in the chest which are audible to the patient. This is almost invariably prc(;cded by a dry cough which may subsequently develop into a productive cough with frothy blood-stained sputum. Breathing becomes unduly laboured and may be gasping and irregular. This may be accompanied by a feeling of fullness and tightness in the chest. As the condition worsens. within hours, the patient becomes cyanosed and anxious, with a subjective lowering of expectation of survival. A low grade fever is usually present and the picture is virtually indistinguishable from a pneumonitis of infective origin.

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106 Acute Pulmonary Oedema al lIigh Allilllde

The conditi on constitutes a life-threatening si tuation. The only hope of sun ival depends upon the concurrent pursuit o f three object ives, namely :-

I. l,fe precipitating factor is hypoxio. A rapid descent must be undertaken with the patient on a stretcher. A patient who may no t be orthopnoeic may become extremely dyspnoeic on the sl ightest exertion. If necessary. this journey must be undertaken in darkness. On Mou nt Kenya, big game will be less ha/..ardolls at night if the descent is as noisy as possible. Pure oxygen must be available. It ca n be administered at an adjusted flow rate depending upon the response of the patient, but in any case has been found to hc of decreasing value as the di sease progresscs (Singh 1965). The administration of oxygen must on no account, therefore, be the reason for a delayed descent. It should be administered during the descent. Descent alone ca n result in remarkably rapid clinical improvement (Steele 1971 ).

2. There is al1 abnormal aecumu/alion offluid ill the lungs. Frusemide produces a marked diuresis with often prompt clinical benefit. It is to be regarded as an essential drug to be admi ni stered on the mountaillside when pulmonary oedema is suspected. Because of the subsequent dehydration which may result . copious fluid s by mouth shou ld be actively encouraged si nce experience has shown that a dehydrated patient will not always ask for water. Oral flu id will not provoke a rela pse of an abnormal accumu lat ion of nuid in the lungs, but it will combat serious dehydration. Tablets (40 mg) should be ava ilable on the mountain and two tahlets should be administered every six hours (Horrobin 1972). Altern at ively, the drug may be administered by intravenous or in tramuscular injection (20 mg in 2 1111). Thi s promotes a speedy diuresis within a few minutes and lasting some four hours.

3. Gas exchallge ;s de/ecI;ve. The use of aminophylline and morphine are wc ll es tablished. Aminophylline. \vhkh may be given by suppository, increases cardiac output "nd in add iti on acts as a hroncholdilator (Brit. med. J . 1973). One of the known effects of morphine is to sh ift blood away from the congt..!sted pulm onary circulalion and thus improvc thc vcnti lation patt ern in thcse patients (Zelis et al 1970). [t is said 10 have an effect which is often dramat ic and has been advocated for this purpose by Singh ct ai, when lIsed in conjunct ion with other remedies. nOlably as Ba tes (1972) dramat ica lly observes, with oxygen a nd frusemide.

The severe case, who does not recover on reaching low altitude, will deteriorate into progressive respiratory acidosis and coma . It is in such patients that urgent hospi ta l­isa tion. if possible by helicopter, is imperative, Intermittent possitive-pressure ventilation (I.P.P.V.) has been fo und to be life-saving in these circumstances . Corretelti ( 1972) advocates the use of octyl alcohol as a safe anli-foam agent 111 conjunctio n with I.P.P.V.

An Africa n, aged 20, belonging to the Teso Tribe turned back at 14,500 feet with vcry severe headache. During an overnight stop at 13,650 feet he developed a continuous cough and bubbling was heard in his chest. Blood-stai ned frothy sputum was no ticed . After admission to hospita l, four hours later, there was rapid and steady clearing of Auid from the lungs during resuscitation with B.O.C. Mark 2 Cyclator automatic lung vent ilator, using alcohol as an anti-foam agent. I re showed complete recovery t\.\,cn ly­cigh t hOllrs after admission (Fig. 2).

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K. Hedges 107

Fig. 2. Chest radiographs. (L) rour hours after admission. (R) Showing complete recovery aftet' 28 hours

Prenntion the primary objective

There appears to be a general agreement that those who arc probably most at risk arc the climbers who ascend rapidly above the critical height of, say, 9,000 feet and remain at or above that altitude for more than onc day. This aspect may in part account for the few evident reports of cases described from the European Alps. A partial expla­nation of the apparent variation in the critical altitude is the descrepancy between calculated and actual barometer pressure in different seasons (Folk 1966).

The normal diuresis associated with adaptioll to altitude, jn combination with exercised-induced sweating and breathing the dry air on high mountains, all contribute a tendency towards dehydration. This is often aggravated by the difficulty of carrying or acquiring sufficient drinking water at altitude. Houston (l971) has stressed that the maintenance of renal efficiency during the initial acclimatisation of the ascent is dependent to a degree upon a sufficient fluid intake, and instances two to three quarts per day, indeed, on Everest, it was found that three to four litres per day were required to maintain a urine output of 1.5 litres per day, and particular attention was given to this on the successful 1953 expedition (Vaughn 1965).

Prophylactic chemotherapy is finding increasing use where the pressures of schedules in modern life are confronted with the need to safeguard health in those who seck high adventure. It has been shown that acetazolamide (Diamox) is an effective protective medication (Forward ct al 1968) which confers significant reductions in the most prominent symptoms of acute mountain sickness. Gray and his co-workers (1971) confirmed the beneht of at:etazolarnide in the prevention of sickness at altitude and Houston elaborates the regime thus: Two or three Diamox tablets taken for two days before and for onc or two days after rapid ascent to above 10,000 feet. The value is believed to lie in its action as a carbonic anhydrase inhibitor and not because of its eITect as a mild diu reLic. lL was considered potentially harmful to prescribe Diamox for longer period s. These rcsearches have also established that Lasix, whilst being an

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108 Acute Pulmollary Oedema at High Altitude

essential drug in the treatment of pulmonary oedema, actually exacerbates the onset if laken as a prophylaclic.

Acute pulmonary oedema is one of a number of non-co mmunicable disorders to which expediti on personnel may be at risk because of activity, climate or terrain . All a re largely preventable if due regard is paid to basic safety considerations.

Acknowledgements

I am indebted to Dr. (Mrsl) J. Haigh of Nanyuki fo r access 10 the clinical da la repon ed in this paper and to Dr. POllle o f the Consolala Mission Hospital, Nyeri, who kindly supplied lhe chesl radiograph s.

Professor Charles S. Houston of the Department of Comlllunity Medici ne. Univer­sity of Vermont, has given considerable assistance in reviewing the literature and I am a lso grateful La him for guidance upon certain points in the text of this paper.

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